Chromatography method and means



June 28, 1966 JENTZSCH ET AL 3,257,775

CHROMATOGRAPHY METHOD AND MEANS Filed Aug. 5, 1965 DIETRICH JENTZSCH WERNER HOVERMANN United States Patent Filed Aug. 5, 1963, Ser. No. 299,707 Claims priority, appliclgtiosi (iermany, Oct. 20, 1962,

5 Claims. (or. 55-67) General The present invention relates to chromatography methods and apparatus and more specifically to the use therein of novel stream splitting particularly useful in accurately controlling the amount of the sample introduced into a chromatographic separating column.

Certain chromatographic separating columns, such as the Golay or Capillary column, have a relatively low capacity for the amount of sample they may receive for analysis. These columns, generally, are in the form of a tube having its inner wall coated with a separating substance thus leaving a free central longitudinal channel.

In order to accommodate such low capacity columns, various designs have been suggested for sample pick-up devices so that small amounts of sample may be introduced into the separating column. It has been found that there is a minimum or lower limit beyond which the amount of the sample cannot be reduced so as to accommodate separating columns having small capacities. To overcome these problems, it has been suggested that a stream splitter be inserted between the sample pick-up device and the separating column. A stream splitter is intended to provide an accurate division or splitting of the carrier gas stream so that a small portion is permitted to enter the separating column while the remainder passes by the column. Usually, the stream split ratio is adjusted by means of an adjustable throttle in the branch of the stream splitter not containing the separating column. This adjustment is made prior to the introduction of the sample into the carrier gas stream. Theoretically, after the sample is introduced into the carrier gas stream it should divide in the same ratio as the ratio of the carrier gas entering the column and the carrier gas bypassing the column prior to the introduction of the sample. For example, if the stream split ratio is set at 1:9 and subsequently a sample of milligrams is introduced, one milligram out of the ten should flow in the separating column and nine milligrams should bypass the separating column. the sample does not divide according to the preset stream split ratio. This is due to the fact that the viscosity of the mixture of carrier gas and sample is different from the viscosity of the carrier gas alone. This change in viscosity alters the control effect of the adjustable throttling member in such a way as to change the stream split ratio to a ratio which differs from the desired pre-set ratio. It is obvious that such changes cause errors in the quantitative analysis being performed by the apparatus.

It is another object of the present invention to provide a new and improved gas chromatography method and means.

It is an object of the present invention to provide a stream splitter arrangement in which the pre-set stream split ratio adjustment is not altered after the introduction of the sample into the carrier gas stream.

In accordance with one aspect, the present invention contemplates a method of separating a sample by chromatography into its constituents in accordance with their physical characteristics comprising the steps of supplying a mixture of sample and carrier fluid, splitting said mixture into parts in a predetermined ratio, separating In practice, it has been found that I by chromatography from one part of said mixture the sample component or components, removing from a second part of said mixture the sampe component or components so that only the carrier component of said second part remains, and utilizing only said remaining carrier component to control the stream-splitting ratio, whereby the stream-splitting ratio is not altered by changes in fluid viscosity.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description, taken in connection with theaccompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing:

FIGURE 1 is a diagram of a gas chromatograph having a stream splitter constructed in accordance with the present invention; and

FIGURE 2 is a sectional view of a portion of a stream splitter constructed in accordance with the present in vention.

Description and operation of the invention Referring to FIGURE 1, a carrier gas stream is intro duced into the gas chromatograph through a pipe 10. This carrier gas stream flows through a sample pick-up device 12, of conventional construction and operation, at which point a sample is added. The mixture of sample and carrier gas flows to a junction 14. At junction 14 the mixture splits into two parts; one part of the mixture flows through a separating column 16 while the remainder flows through a pipe 20. That portion of the mixture flowing through the separating column 16 flows to a detector 18, which may be a flame ionization detector of conventional construction and operation. The part of the mixture flowing through pipe 20 continues on through a U-shaped tube 22 filled with a suitable filtering material to a throttling member 24, which may be a needle valve, and on to an output port 26.

Referring to FIGURE 2, the U-shaped tube 22 is shown as being closed at its two ends by a pair of plugs 28 and 30. Each of these plugs is provided with a narrow central bore 32 and 34, respectively, opening into recesses for pipes 20 and 36, respectively. A pair of sieves 38 and 49 are provided in front of the inner port of the bores 32 and 34, respectively, to prevent the filtering material in the U-shaped tube 22 from entering the bores and clogging them. Pipe 36 leads to the needle valve throttling member 24 which may be adjusted by means of an adjusting knob 42.

The filtering material contained within the 'U-shaped tube 22 is of such characteristics that it is effective to remove the sample in that part of the mixture which flows through tube 20. Activated charcoal is a suitable material for removing the sample. By locating the U-shaped tube 22 upstream from the throttling member 24, only pure carrier gas reaches the throttling member. Thus, the stream reaching the throttling member 24 has the same viscosity before and after injection of the sample so that the ratio of stream splitting is the same before and after the sample is introduced.

The introduction of the U-shaped tube 22 does not disturb the stream split ratio since the flow resistance of this tube, with respect to the sample, is constant and is negligible in comparison to the flow resistance of the throttiing member 24.

While there has been described what is at present considered a preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, intended to cover all such changes and modifications as fall within the true spirit and scope of the invention as defined by the appended claims.

What is claimed is: 1. In the method of separating a fluid sample by chromatography into its constituents in accordance with their physical characteristics by passing the sample through chromatography separation means, the steps of:

supplying a mixture of sample and carrier fluid, splitting said mixture into parts in a predetermined ratio,

removing from one part of said mixture the sample component or components so that only the carrier component of said one part remains,

utilizing only said remaining carrier component to control the stream-splitting ratio, whereby the actual stream-splitting ratio is substantially unaffected by a difference of viscosity of the carrier component as compared with that of the mixture of sample component and carrier component, and passing the other part of said mixture to said separation means.

2. In apparatus for separating a fluid sample by chromatography into its constituents in accordance with their physical characteristics comprising:

chromatography separation means,

means for supplying a mixture of sample and carrier means for splitting said mixture into parts in a predetermined ratio,

means for removing from one part of said mixture the sample component or components to supply at the output of said last-mentioned means only the carrier component of said one part,

means coupled to said output of said last-mentioned 'means and responsive only to the carrier component supplied at said output for controlling the mixturespliting ratio substantially without error due to a difference of viscosity of the carrier component as compared with that of the mixture of sample component and carrier component, and means for coupling the other part of said mixture to said separation means.

3. In apparatus for separating a gas sample by gas chromatography into its constituents in accordance with their physical characteristics comprising:

means for supplying a mixture of sample and carrier means for splitting said mixture into two parts in a predetermined ratio,

means for separating by gas chromatography from one part of said mixture the sample component or components,

filter means for removing from the second part of said mixture the sample component or components to supply at the output of said last-mentioned means only the carrier component of said second part,

and means coupled to said output of said last-mentioned means and responsive only to the carrier component supplied at said output for controlling the mixturesplitting ratio substantially without error due to a difference of viscosity of the carrier component as compared with that of the mixture of sample component and carrier component.

4. Apparatus for separating a gas sample by gas chromatography into its components in accordance with their physical characteristics, comprising:

means for supplying a mixture of sample gas and carrier means including a junction for splitting said mixture into a first part and a second part in a predetermined ratio,

a first branch coupled to said junction to receive said first part and including means for separating by gas chromatography from said first part the sample component or components,

a second branch coupled to said junction to receive said second part,

filter means within said second branch for removing from said second part the sample component or components to supply at the output of said filter means only the carrier component of said second part,

and means within said second branch and coupled to said output of said filter means and responsive solely to said carrier component supplied at said output for controlling the mixture-splitting ratio substantially without error due to a difference of viscosity of the carrier component as compared with that of the mixture of sample component and carrier component. 5. Apparatus according to claim 4 wherein said control means comprises a throttling device.

References Cited by the Examiner UNITED STATES PATENTS 5/1961 Boeke 67 X 10/1962 Brenner 55-386 OTHER REFERENCES REUBEN FRIEDMAN, Primary Examiner. 

1. IN THE METHOD OF SEPARATING A FLUID SAMPLE BY CHROMATOGRAPHY INTO ITS CONSTITUENTS IN ACCORDANCE WITH THEIR PHYSICAL CHARACTERISTICS BY PASSING THE SAMPLE THROUGH CHROMATOGRAPHY SEPARATION MEANS, THE STEPS OF: SUPPLYING A MIXTURE OF SAMPLE AND CARRIER FLUID, SPLITTING SAID MIXTURE INTO PARTS IN A PREDETERMINED RATIO, REMOVING FROM ONE PART OF SAID MIXTURE THE SAMPLE COMPONENT OR COMPONENTS SO THAT ONLY THE CARRIER COMPONENT OF SAID ONE PART REMAINS, UTILIZING ONLY SAID REMAINING CARRIER COMPONENT TO CONTROL THE STREAM-SPLITTING RATIO, WHEREBY THE ACTUAL STREAM-SPLITTING RATIO IS SUBSTANTIALLY UNAFFECTED BY A DIFFERENCE OF VISCOSITY OF THE CARRIER COMPOENT AS COMPARED WITH THAT OF THE MIXTURE OF SAMPLE COMPONENT AND CARRIER COMPONENT, AND PASSIG THE OTHER PART OF SAID MIXTURE TO SAID SEPARATION MEANS. 